1. Wonkwang Digestive Disease Research Institute, Iksan, Jeonlabuk-do, Korea
2. Good Breath Clinic, Gunpo, Gyeonggi-do, Korea
3. Department of Gastroenterology, Okazaki City Medical Association Public Health Center, Okazaki, Japan
4. Department of Gastroenterology and Metabolism, Nagoya City University Graduate School of Medical Science, Nagoya, Japan
5. Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
6. Division of Gastroenterology and Hepatology, Department of Medicine, National University Hospital, Singapore
7. Department of Gastroenterology, School of Medicine, Wonkwang University, Iksan, Jeonlabuk-do, Korea